In electronic devices such as mobile computers, personal computers, and car navigation systems, touch panels which allow data to be inputted by detecting a touch position of contact with a fingertip, a pen point, or the like while an image on a display screen of a liquid crystal display device or the like is being viewed have recently become widely used.
For example, Japanese Unexamined Patent Application Publication No. 2015-122057 discloses a display device including: a lower substrate; a gate line formed over the lower substrate so as to extend in a second direction (transverse direction); a gate insulating layer formed over the gate line; a data line formed over the gate insulating layer so as to extend in a first direction (longitudinal direction); a first protective layer formed over the data line; a pixel electrode and a signal line formed over the first protective layer in each pixel area; a second protective layer formed over the pixel electrode and the signal line; one electrode formed over the second protective layer so as to serve as a common electrode and a touch electrode; a liquid crystal layer formed over the electrode; and an upper substrate formed over the liquid crystal layer and provided with a black matrix, a color filter, and the like.
Further, for example, Japanese Unexamined Patent Application Publication No. 2009-058913 discloses a liquid crystal display device including: a liquid crystal display panel including a first substrate, a second substrate, and liquid crystals sandwiched between the first substrate and the second substrate, the liquid crystal display panel including a plurality of pixels arranged in a matrix. In the display device, the first substrate has a laminated structure of a first transparent electrode, a first insulating film, a second transparent electrode, a second insulating film, and a third transparent electrode in a transparent display area provided in at least part of each of the pixels, the first transparent electrode, the first insulating film, the second transparent electrode, the second insulating film, and the third transparent electrode being laminated in descending order of proximity to the first substrate, the first transparent electrode and the second transparent electrode are electrically insulated from each other and form a first retention capacitor via the first insulating film, and the second transparent electrode and the third transparent electrode are electrically insulated from each other and form a second retention capacitor via the second insulating film.